GB1589767A - Magnetic lifting devices - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO MAGNETIC LIFTiNG DEVICES (71) We, W. E. BURNAND & SON LIMITED, a British Company, of Duo Works, Shoreham Street, Sheffield, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be per- formed, to be particularly described in and by the following statement: The invention relates to magnetic lifting devices and has for its object to provide an improvement therein.

According to the invention, there is provided a magnetic lifting device including a metal casing; two permanent magnets or two rows of permanent magnets disposed within the casing and being laterally spaced relative to each other relative and to side walls of the casing; a yoke member connecting the lower ends of the magnets or rows of magnets; excitation coils surrounding the magnets or rows of magnets; and switch means whereby, in response to at least one pulse of D.C. current in the coils the magnetism set up in the two magnets or two rows of magnets, as the case may be, can be of like polarity so that the lower ends of the magnets or rows of magnets, in association with the lower ends of the adjacent walls of the casing, exhibit an outside magnetic field and the device is operative, or can alternatively be of unlike polarity so that the lower ends of the magnets or rows of magnets are magnetically short circuited by the yoke member which connects them and the device is inoperative. A pole shoe will preferably bear against the underside of the yoke member connecting the lower ends of the magnets or rows of magnets.Preferably, also, pole elements will be secured to the lower edges of the side walls of the metal casing, the pole shoe being aligned with but spaced from said pole elements.

Stainless steel bolts may extend through the pole shoe, the yoke member, and the permanent magnets to hold the device together. Upper surfaces of the permanent magnets may bear against pole pieces which themselves bear against a top plate of the metal casing. Apertured lifting lugs may be secured to the top plate of the metal casing.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the drawings accompanying the Provisional Specification, in which: Fig. 1 is a longitudinal section through a magnetic lifting device embodying the invention Fig. 2 is a sectional view on the line 2-2 in Fig. 1, and Figs. 3 and 4 are diagrammatic views on the underside of the device which will be referred to presently.

Referring now to Figs. 1 and 2 of the drawings, the lifting device there illustrated includes an outer casing made of metal plate, the casing including a top plate 10 to which pairs of apertured lifting lugs 12 are welded, end plates 14 and side plates 16.

Permanent magnet blocks 18 are contained within the casing and are disposed in two laterally spaced rows 20 and 22 as shown in Fig. 2. A yoke member 24 contacts the lower surfaces of the rows of magnet blocks and spans the space between them. The upper surfaces of the rows of magnet blocks bear against pole pieces 26 which themselves bear against the top plate of the casing.

A pole shoe 28 bears against the underside of the yoke member and stainless steel bolts 30 extend through said pole shoe, yoke member, magnet blocks and pole pieces to retain them in position. As shown in Fig. 2, the pole shoe is aligned with but spaced from pole elements 32 which are secured to the lower edges of the side plates of the casing.

Excitation coils 34 and 36 surround the rows of permanent magnet blocks 20 and 22 and switch means (not shown) are provided whereby D.C. electric current can flow either as shown in Fig. 3 or as shown in Fig. 4. Consequently, in response to a pulse or a number of pulses of D.C. current in the coils through the circuit indicated in Fig. 3 the magnetism set up in the rows of magnet blocks can be of like polarity so that the lower ends of the rows of magnet blocks, in association with the pole elements 32 at the lower edges of the side plates of the casing, exhibit an outside magnetic field and the device is operative to lifl a ferrous metal plate or the like.

Alternalively in response to a pulse of D.C. current in the coils through the circuit indicated in Fig. 4 the magnetism set up in the rows of magnet blocks can be of unlike polarity so that the lower ends of the magnet blocks are magnetically short circuited by the yoke member 24 and the device is inoperative so that whatever ferrous metal load has been suspended by the lifting device is then released.

It will be understood that since the lifting device can only be changed from opera tivc to inoperative condition or from inoperative to operative condition by a pulse of electiic current it is inherently very safe in operation because a failure of the electric current supply cannot result in the accidental release of a suspended load.

It will also be seen that the device possesses no moving parts (other than the moving contacts within the switch means) so that the device can be expected to have a long trouble free life. The device can of course he made of virtually any required size for lifting whatever loads are required to be lifted, the size and number of the magnet blocks being suitably selected.

The selection of suitable materials for tlic permanent magnet blocks and for the yoke member and pole pieces will present no problem to those skilled in the art. It will also be understood that the intensity and duration of the pulse or pulses of D.C. current required to render the device operative or inoperative may be calculated by a person skilled in the art or may be determined by trial and experiment.

WHAT WE CLAIM IS:- 1. A magnetic lifting device including a metal casing; two permanent magnets or two rows of permanent magnets disposed within the casing and being laterally spaced relative to each other and relative to side walls of the casing; a yoke member con necking the lower ends of the magnets or rows of magnets; excitation coils sur rounding the magnets or rows of magnets; and switch means whereby, in response to at least one pulse of D.C. current in the coils the magnetism set up in the two magnets or two rows of magnets, as the case may be, can be of like polarity so that the lower ends of the magnets or rows of magnets, in association with the lower ends of the adjacent walls of the casing, exhibit an outside magnetic field and the device is operative, or can alternatively be of unlike polarity so that the lower ends of the magnets or rows of magnets are magnetically short circuited by the yoke member which connects them and the device is inoperative.

2. A magnetic lifting device according to claim 1, in which a pole shoe bears against the underside of the yoke member connecting the lower ends of the magnets or rows of magnets.

3. A magnetic lifting device according to clairn 2, in which pole elements are secured to the lower edges of the side walls of the metal casing, the pole shoe being aligned with but spaced from said pole elements.

4. A magnetic lifting device according to either one of claims 2 and 3, in which stainless steel bolts extend through the pole shoe, the yoke member, and the permanent magnets to hold the device together.

5. A magnetic lifting device according to any one of the preceding claims, in which upper surfaces of the permanent magnets bear against pole pieces which themselves bear against a top plate of the metal casing.

6. A magnetic lifting device according to claim 5, in which apertured lifting lugs are secured to the top plate of the metal c asing.

7. A magnetic lifting device constructed, arranged and adapted to operate substantially as hereinbefore described with ref erenee to and as illustrated by the drawings accompanying the Provisional Specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. in Fig. 3 the magnetism set up in the rows of magnet blocks can be of like polarity so that the lower ends of the rows of magnet blocks, in association with the pole elements 32 at the lower edges of the side plates of the casing, exhibit an outside magnetic field and the device is operative to lifl a ferrous metal plate or the like. Alternalively in response to a pulse of D.C. current in the coils through the circuit indicated in Fig. 4 the magnetism set up in the rows of magnet blocks can be of unlike polarity so that the lower ends of the magnet blocks are magnetically short circuited by the yoke member 24 and the device is inoperative so that whatever ferrous metal load has been suspended by the lifting device is then released. It will be understood that since the lifting device can only be changed from opera tivc to inoperative condition or from inoperative to operative condition by a pulse of electiic current it is inherently very safe in operation because a failure of the electric current supply cannot result in the accidental release of a suspended load. It will also be seen that the device possesses no moving parts (other than the moving contacts within the switch means) so that the device can be expected to have a long trouble free life. The device can of course he made of virtually any required size for lifting whatever loads are required to be lifted, the size and number of the magnet blocks being suitably selected. The selection of suitable materials for tlic permanent magnet blocks and for the yoke member and pole pieces will present no problem to those skilled in the art. It will also be understood that the intensity and duration of the pulse or pulses of D.C. current required to render the device operative or inoperative may be calculated by a person skilled in the art or may be determined by trial and experiment. WHAT WE CLAIM IS:-

1. A magnetic lifting device including a metal casing; two permanent magnets or two rows of permanent magnets disposed within the casing and being laterally spaced relative to each other and relative to side walls of the casing; a yoke member con necking the lower ends of the magnets or rows of magnets; excitation coils sur rounding the magnets or rows of magnets; and switch means whereby, in response to at least one pulse of D.C. current in the coils the magnetism set up in the two magnets or two rows of magnets, as the case may be, can be of like polarity so that the lower ends of the magnets or rows of magnets, in association with the lower ends of the adjacent walls of the casing, exhibit an outside magnetic field and the device is operative, or can alternatively be of unlike polarity so that the lower ends of the magnets or rows of magnets are magnetically short circuited by the yoke member which connects them and the device is inoperative.

2. A magnetic lifting device according to claim 1, in which a pole shoe bears against the underside of the yoke member connecting the lower ends of the magnets or rows of magnets.

3. A magnetic lifting device according to clairn 2, in which pole elements are secured to the lower edges of the side walls of the metal casing, the pole shoe being aligned with but spaced from said pole elements.

4. A magnetic lifting device according to either one of claims 2 and 3, in which stainless steel bolts extend through the pole shoe, the yoke member, and the permanent magnets to hold the device together.

5. A magnetic lifting device according to any one of the preceding claims, in which upper surfaces of the permanent magnets bear against pole pieces which themselves bear against a top plate of the metal casing.

6. A magnetic lifting device according to claim 5, in which apertured lifting lugs are secured to the top plate of the metal c asing.

7. A magnetic lifting device constructed, arranged and adapted to operate substantially as hereinbefore described with ref erenee to and as illustrated by the drawings accompanying the Provisional Specification.